New treatment combination for rectal cancer patients offers improved rates of remission
Published: 4 May 2025
A new trial of patients with advanced rectal cancer has found that the addition of immunotherapy treatment alongside extended radiotherapy led to better rates of remission
A new trial of patients with advanced rectal cancer has found that the addition of immunotherapy treatment alongside extended radiotherapy led to better rates of remission.
The findings from the UK-wide trial – released today at the ESTRO 2025 conference in Vienna – reported high rates of complete response to treatment among rectal cancer patients participating in the trial, particularly in the group where immunotherapy was combined with short course radiotherapy.
Overall, a high rate of 52% complete remission was observed in patients across the trial, exceeding pre-trial expectations of 30%.
The randomised phase II PRIME-RT trial, led by the University of Glasgow and NHS Greater Glasgow & Clyde, tested extended pre-surgical radiotherapy regimens, both of short course and long course periods, used in addition to immunotherapy in patients with locally-advanced rectal cancer (patients with larger and more aggressive tumours), marking the first time this combination of treatments has been evaluated in the same patient population.
The trial also found that the addition of immunotherapy treatment for these patients did not appear to significantly add any negative side effects.
Rectal cancer kills around 4,100 people in the UK (around 410 in Scotland) every year. Over the last 20 years, incidence of early-onset rectal cancer has increased by 50.5% in the UK (53.6% in Scotland) for people aged 25-49 and rates are rising faster in young women than young men, particularly in Scotland and Northern Ireland.
Each year around 12,000 people are diagnosed with rectal cancer in the UK. Around 1,100 people are diagnosed each year in Scotland. Bowel cancer, also known as colorectal cancer, is the second most common cause of cancer deaths in the UK. Rectal cancer makes up around a quarter of bowel cancer deaths.* Despite this, treatment options remain limited, particularly for patients who are diagnosed at later stages of the disease.
The usual treatment for rectal cancer is surgery, with most patients requiring a temporary stoma or ostomy. Up to one third of patients with colorectal cancer often require a permanent colostomy.
Seeking to find better treatments and outcomes for patients the phase II PRIME-RT trial investigated the possibility of increasing the number of patients with complete remission from the disease, using a combination of immunotherapy and radiotherapy, whilst also avoiding the need for surgery.
The trial involved 46 patients across multiple centres across the UK for whom their rectal cancer was locally-advanced. The trial tested two different radiotherapy strategies – short and long-course regimes – in combination with Durvalumab, a common immunotherapy treatment. For patients reaching the end of treatment, high rates of complete remission were observed in both of the two arms of the trial (67% and 48%); and at 18 months follow-up, 56% and 33% of patients respectively exhibited sustained complete responses.
Chief Investigator of the trial, Campbell Roxburgh, Professor of Colorectal Surgical Oncology at the University of Glasgow’s School of Cancer Sciences, said: “We are extremely encouraged by the findings of our PRIME-RT trial, which provides positive evidence of a more successful treatment option for patients with advanced rectal cancer.
“Our trial specifically aimed to increase rates of complete remission in these patients, and to allow more patients to be managed without the need for life-altering surgery. The success of our findings went beyond our expectations, adding to growing evidence that immunotherapy synergises with radiotherapy regimens to enhance rates of remission in this group of patients. In particular, our findings add weight to emerging evidence that indicate a short-course radiation schedule may represent the best treatment partner for immunotherapy.
“Going forward, we are planning follow-up trials in rectal cancer, with the aim of further enhancing responses informed by these results. Although patient response rates have improved, some patients still do not respond completely to these treatments and continue to require surgery. More still needs to be done to understand the biology underpinning treatment response, to help us to deliver a more ‘precision medicine’ biology approach to rectal cancer.”
The phase II PRIME-RT trial is funded by AstraZeneca UK and was carried out in collaboration with Glasgow’s Experimental Cancer Medicine Centre (ECMC). Glasgow’s ECMC is funded by a partnership between Cancer Research UK, the Scottish Government Chief Scientist Office and the Little Princess Trust. The trial was led by the University of Glasgow and NHS Greater Glasgow & Clyde in collaboration with The Christie NHS Foundation Trust, NHS Grampian, The University of Aberdeen, the University of Oxford and NHS Ayrshire and Arran.
Cancer Research UK Director of Research, Dr Catherine Elliott, welcomed the news and said: “Harnessing our own immune system to help us tackle cancer is a growing area of cancer research and in combination with other therapies, such as radiotherapy, it can be even more effective.
“It’s encouraging news that this clinical trial combining these therapies can not only reduce the need for life-changing surgery but can help increase the number of people with rectal cancer in remission.”
Enquiries: ali.howard@glasgow.ac.uk or elizabeth.mcmeekin@glasgow.ac.uk
First published: 4 May 2025